Ale drinking, dancing and general merry making was the way of the Norse, who observed several particular customs at this time of year, including boiling up half a cow's head and using the cleaned skull as a candlestick holder.
In Shetland, where the Vikings dominated from 800 AD for almost 500 years, these ways were celebrated on the islands until the end of the 18th Century.
Islanders mixed the Christian customs of Christmas with the old way of Yule until the late 1700s, wrote James R. Nicolson in Shetland Folklore.
He said: "People continued to dance and make merry, although for a few short hours they paused in their revels and remembered the birth of Christ.
Yule truly began on the Winter Solstice, which this year falls on Sunday, December 22, but the festivities kicked off seven nights before then day known as Tul-yas-e’en.
On that night, it is believed the trows, a mischievous spirit in the folklore of the Northern Isles, received permission to leave their underground homes and visit island houses.
Tul-yas-e’en was followed by Helya’s Nicht, when a special meal of milk and meal was eaten and the children were committed to the care of Midder Mary – The Virgin Mary – another relic of Roman Catholic days that survived a surprisingly long time, Nicolson wrote.
Next came Tammasmas E’en, which was particularly holy, and no work of any kind was permitted that night - or any kind of amusement.
The Sunday before Yule was another important day. Called Byana’s Sunday - or Prayer Sunday - half a cow’s head was boiled and eaten for supper that night.
The skull was carefully cleaned and with a candle stuck in the eye socket was laid aside to be used a few days later.
The eve of Yule - or Yule E'en was typically a day of preparation.
Bread would be baked as usual in the morning and was followed by a round of oatcakes - or Yule Cakes - being put in the oven for each child of the house.
The cakes were pinched into points around the edge and a hole was made in the centre.
"These were called Yule cakes, and we no doubt originally symbolic of the sun now returning," Nicolson wrote.
On Yule E’en, each member of the family washed themselves and put on a clean item of clothing, to sleep in.
But first, a ritual came before bed.
Hands or feet were put into water with three burning blazing bits of peat dropped into the water.
It was believed that the trows - those mischievous spirits - could take the power from the foot or hand if the ritual was not followed.
Then, according to Jessie M.E. Saxby in Shetland Traditional Lore, the house was tidied with no Christian thing left in sight.
All locks were opened and a lamp left burning through the night.
Before daylight on Yule morning, the head of the house lit the candle which had been stuck in the eye socket of the skull.
He then used it to lead the way to the byre, where the cattle was fed - a little bit more than usual - by its light.
On his return to the house, a yule dram was handed to the people of the house – and special neighbours – with children too offered a sip.
No work of any kind was done on Yule Day, with football played by men and dancing, games and singing found in houses all over Shetland.
The rituals and customs were stuck to seriously, with it feared the smallest deviation might bring misfortune to the whole household.
One of the most important observances of the whole Yule period was the saining ritual that safeguarded life and property.
At sunset, two pieces of straw were taken from the yard and laid in the form of a cross at the stile at the entrance to the cornyard.
Hairs drawn one from each cow on the croft were plaited and fastened above the door of the byre and a lowin taand - or blazing peat - carried through all the outhouses.
For the next seven days, it was believed no work should be undertaken with bad luck looming for a year for those who took to their trade.
One account warns that two fishermen who went out on the fourth day of Yule were met with a horrible sea creature, which was partly a horse.
On New Year's Day, a little work, such as mending, cleaning and perhaps a little fishing was permitted.
From that day until Up Helly A- the 24th night of Yule, work and play went hand in hand, according to Nicolson.
House parties got bigger and people started gathering in barns. Dancing was 'vigourous' and the times indeed seriously merry.